Population-based surveys estimate that the prevalence of methamphetamine use is 20 times higher among men who have sex with men (MSM) compared to the general population. Methamphetamine- associated sexual risk behavior is also a driving force in the MSM HIV epidemic: methamphetamine use has been associated with unprotected sex, increased number of sex partners, and sexually transmitted infections, including HIV. In parallel with the continued testing of behavioral approaches, we believe the time has come to test the feasibility and acceptability of pharmacologic interventions to reduce methamphetamine use among MSM. Preliminary dosing studies demonstrate that aripiprazole (Abilify), an FDA-approved, well- tolerated antipsychotic, and partial dopamine agonist, reduced the effects of methamphetamine in humans, and exhibited a good safety profile. We propose to expand upon these promising results by conducting a randomized, double-blind, placebo-controlled pilot study of aripiprazole among sexually-active, methamphetamine-dependent MSM. The specific aims of this pilot study are: 1) To assess the feasibility of enrolling and retaining methamphetamine-dependent MSM into a randomized, double-blind study of aripiprazole versus placebo that includes biologic (urine methamphetamine testing) and behavioral (sexual risk) measures. 2) To compare the acceptability and tolerability of aripiprazole versus placebo among methamphetamine- dependent MSM, as determined by the proportion of adverse clinical events and adherence (by self-report and electronic pill caps) to medication in the aripiprazole and placebo groups. 3) To explore whether aripiprazole reduces methamphetamine use significantly more than placebo among methamphetamine-dependent MSM, as determined by the proportion of methamphetamine-negative urines and by self-report of methamphetamine use in the aripiprazole versus placebo group. If promising, study results will be used to design larger, definitive clinical trials to determine the efficacy of aripiprazole in reducing methamphetamine use and corresponding methamphetamine-associated sexual risk among MSM. [unreadable] [unreadable] [unreadable]